Percussion tool control means



Sept. 2, 1969 A. w. WALLACE PERCUSSION TOOL CONTROL MEANS 2 Sheets-Sheet1 Filed NOV. 16, 1967 as 4 a4 so INVENTOR. ARTHUR M! WALLACE p 2, 1969A. w. WALLACE 3,464,500

PERCUSSION TOOL CONTROL MEANS Filed Nov. 16, 1967 2 Sheets-Sheet 2 nitsStates ABSTRACT OF THE DISCLOSURE A motor control valve for percussiontools, such as rock drills, operable to idle or shut down the percussionmotor when the tool shank is not in position to be struck by thereciprocating hammer of the motor. One embodiment consists of apneumatic actuator for the motor control valve which receives a pressuresignal via a hole cleaning tube which telescopically fits in the toolshank. When the tool shank moves out of hammer striking position thepressure signal, normally communicated through the hole cleaning tube,is interrupted thereby permitting the actuator to close the motorcontrol valve to throttle the supply of motive air to the motor. Shouldthe cleaning medium be liquid, a mechanical actuator is employedconsisting of a hole cleaning tube having a motor valve elementconnected at one end and being connected to the tool shank for closingthe motor valve when the shank moves out of hammer striking position.

Background of the invention Conventional pneumatic percussion tools suchas rock drills commonly comprise a percussion motor having a cylinderand pneumatically reciprocated piston hammer disposed in the cylinder. Asection of the working implement known as the shank is chucked in oneend of the cylinder for limited axial movement and has one end designedto be struck by the piston hammer to transmit the percussive energy tothe bit end of the working implement. Control of the motive fluid isusually accomplished by a manually operated throttle valve.

In applying the tool to the work, the shank is usually kept in strikingposition by continuously feeding the drill toward the work. However,often is the case when the feed rate is not suflicient to keep up withthe drill penetration rate or a fault in the work material allows theshank to move forward out of piston hammer striking position. To preventovertravel and impact of the piston hammer against the cylinder end Wallunder the aforementioned circumstances, a protective pneumatic cushionchamber formed in the cylinder ahead of the piston hammer absorbs thekinetic energy of the hammer and serves as a rebound cushion to urge thehammer in the opposite direction.

One problem that results from utilizing the pneumatic cushionextensively is that the repeated compression of air trapped in thecushion chamber results in substantial temperature increase of thesurrounding parts as they absorb the heat of compression from thetrapped air. Also, a dangerous condition often results due to thepresence of drill lubricating oil in the trapped air forming acombustible mixture susceptible to compression ignition. This unwantedcombustion of the air-oil mixture in the hammer cushion is not onlyuncontrollable but almost invariably results in serious damage to thedrill such as causing the hammer to seize in the cylinder, overheatingand damage to other surrounding parts, and the creation of a hazardouscondition to the drill operating personnel.

So rapidly does this phenomenon occur that a drill operating at or nearfull throttle will usually experience a heat-induced failure before thethrottle can be closed atent Patented Sept. 2, 1969 even in the hands ofa skilled operator. It is therefore particularly desirable to haveautomatic throttling control means immediately responsive to the shankbeing out of striking position to shut down or idle the drill percussionmotor.

Another benefit of a control of the type described above is realizedwhen pulling the drill steel from the hole. In the pulling operation thereverse feeding of the drill will also result in the shank moving out ofhammer striking position. Automatic throttling of drill motive air willreduce total air consumption during that portio of the drilling cycle,and eliminate excessive vibration due to the reaction forces of thepiston hammer cushion chamber as well as prevent the aforementionedoverheating problem.

Summary of the invention The invention has as a principal object theprovision of automatic control means for idling or shutting down apercussion tool of the type described in response to axial displacementof the tool shank from hammer striking position.

It is also an object of the invention to provide automatic means foridling the drill percussion motor during backing out or drill steelpulling operations.

A further object is the provision of automatic control means for idlingor shutting down a drill percussion motor due to a failure of a cleaningfluid conduit seal or due to inadequate cleaning fluid pressure.

A still further object of the invention is the provision of automaticthrottle control means to assure safe operation of the associated drilland prevent damage to the drill component parts resulting fromcompression ignition of the air-oil mixture comprising the percussionmotor pneumatic cushion.

In one embodiment the throttling valve is actuated by a pneumatic pistonresponsive to the supply thereto of cleaning fluid through a doublewalled hole cleaning tube. The cleaning tube coacts with the shank tosense the position of said shank relative to the percussion hammerwhereby cleaning fluid is supplied to the actuator.

An alternate embodiment utilizes the hole cleaning tube itself as amechanical throttlin valve actuator. The drill steel shank frictionallyengages the cleaning tube while the opposite end of the tube is attacheddirectly to a throt tling valve located upstream of the percussionmotor. Both the valve element and the cleaning tube moveably responddirectly to changes in shank position.

The embodiments disclosed provide effective automatic control meanswhich are simple and reliable in construction and operation.

The novel features as well as the objects and advantages of theinvention will be well understood upon reading the following detaileddescription accompanied by the drawings, wherein like referencecharacters are used to designate similar parts.

Brief description of the drawings FIG. 1 is a longitudinal section of atypical independent rotation percussion rock drill assembly illustratingthe preferred control components in position to admit motive air to thedrill percussion motor.

FIG. 2 is a fragmentary longitudinal section of the assembly of FIG. 1illustrating the drill steel shank out of striking position and thecontrol conduit vented.

FIG. 3 is a fragmentary longitudinal section of the assembly of FIG. 1with the control valve in a closed position in response to the conditionof the shank as shown in FIG. 2.

FIG. 4 is a transverse section through the double walled cleaning fluidtube taken along the lines 4-4 of FIG. 2.

FIG. 5 is a transverse section taken along the lines '55 of FIG. 3illustrating the control valve chest and various fluid passagestherethrough.

FIG. 6 is a partial longitudinal section of a rock drill similar in manyrespects to the drill shown in FIG. 1 but illustrating a mechanicallyactuated version of the subject control means and is split along theaxis 77 to show the two working positions of the control.

Description of the preferred embodiments Referring to FIGS. 1, 2 and 3the illustrated drilling device is a percussion drill of the independentrotation type. In FIG. 1 the drill percussion motor is illustratedhaving a housing 10 with a cylinder bore 12 therethrough and areciprocably disposed piston hammer 14. A distributing valve assembly 16is operative to alternately supply motive air to opposite sides 18 and20 of the hammer 14 for a power stroke and return stroke, respectively.An exhaust port 22 in the cylinder housing 10 vents spent motive air tothe atmosphere at the end of each hammer stroke. The hammer 14 has astem 24 extending through a wear bushing 26 which in turn is housed in acylinder sleeve 28. The hammer stem 24 also extends partially through achuck driver 30 to the striking end 32 of the stem 24 which is shown inengagement with a cooperating striking surface 34 of a short section ofdrill steel known as the shank 36. The drill steel shank is retained forlimited axial movement in a chuck 38 having internal splines 40 engagingcomplementary external splines 42 on the shank 36. The chuck 38 isrotatively drivable by the chuck driver 30 through mechanically engagingteeth, not shown, and the chuck 38 in turn rotates the shank 36. Drillsteel rotation power is supplied by a pressure fluid motor andtransmission generally designated by 44 through a drive shaft 46 to asecond transmission of which the chuck 38 and driver 30 form a part, thedriver 30 being supported on bearings 48 and also comprising a spur gear50.

As previously mentioned, the shank 36 is mounted in the chuck 38 forlimited axial movement so that percussive blows from the piston hammer14 may be transmitted solely to the drill steel. The shank 36 is,however, retained in the drill by a cap 52 threadably attached to achuck end housing 54 and is limited in its movement toward the pistonhammer 14 by the splines 42 engaging a bushing 56 in the chuck driver30. It will be noted that the splines 42 on the shank 36 and the stem 24of the piston hammer are dimensioned such that the shank 36 may movelongitudinally out of reach of the striking face 32 on the stem 24before coming into contact with the cap 52. The hammer 14 is limited inits forward travel under the circumstances by a pneumatic cushion 58formed by the cylinder bore 12 and the face 60. As the hammer 14 travelstoward the face 60, the piston face 20 will close off supply ports forreturn stroke motive air, not shown. As the volume of the chamber 58decreases a corresponding pressure increase will result, eventuallyreaching a value suflicient to halt the forward travel of the hammer 14and return it toward the distributing valve 16 prior to commencement ofanother power stroke.

The shank 36 has a hollow interior 62 for conducting drill hole cleaningfluid such as compressed air or water through the drill steel to thehole for flushing drill cuttings during drilling operations. A slightlyenlarged bore 64 in the shank 36 telescopically receives an elongatedcleaning fluid tube member generally designated by 66 which eX- tendsthrough the drill assembly to the rotation motor end housing 68 where itterminates with a tube head 70. The cleaning fluid tube 66 is retainedin the drill assembly by a threaded nut 72 and packing 74. Cleaningfluid such as compressed air is introduced from a suitable sourcethrough a hose assembly 76.

Referring to the shank end of the cleaning fluid tube 66, a resilientsealing element 78 housed in the shank bore 64 sealingly engages theouter diameter of the tube 66 but is relatively slidable thereto andprevents leakage of cleaning fluid into the chuck end of the drill whichis vented 4 through the chuck driver 30 at 80 and the chuck end hous ing54 at 82.

The cleaning fluid tube 66 is of double walled construction having aninterior passage 84 for the main flow of cleaning fluid, and an annularflow passage 86 formed by the inner tube 88 and outer tube 90. Theannular flow passage 86 is sealed at the shank end by flaring the innertube 88 tightly against the outer tube 90 by suitable means. Theopposite end of the passage 86 is sealed by the tube head 70. Smallradial ports 92 at the shank end of the tube 66 are located to allowcleaning fluid under pressure to communicate with the flow passage 86(see FIG. 4) and to flow through the same toward the back end of thepercussion motor housing 10 where ports 94 communicate with an actuatorchamber 96 formed as part of a control valve chest 98, and a cover 100.As can be seen in FIG. 1 and FIG. 3 the control valve chest 98 isinterposed between the motive air inlet port 102 and the percussionmotor distributing valve 16. A valve spool 104 is connected to anactuator piston 106 reciprocably disposed in the chamber 96. A vent 108keeps one side of the piston 106 at atmospheric pressure.

The position of the control valve spool 104 in FIG. 1 corresponds tonormal operation of the percussion drill. In this condition the drill,mounted on a guide shell and feed assembly (not shown), would be fedtoward the workface and the shank 36 would be maintained inblowreceiving relationship with the piston hammer 14. Cleaning fluidunder pressure from the interior 84 of the tube 66 would also, by way ofports 92, flow through the annular passage 86 to the actuator chamber 96causing the piston 106 to hold the valve spool 104 in the open positionshown allowing full flow of motive air through the passages 110 and 112past the valve spool 104 and on to the distributing valve via passages114, 116 and 118 (see FIG. 5) to operate the percussion motor.

However, if the drill steel and shank 36 should strike a fault or voilin the drill workings or undergo a breakage of the drill steel, theshank 36 would be driven forward by the piston hammer 14 and remain outof striking relationship thus causing the cushion chamber 58 to absorbthe kinetic energy of the piston hammer 14 during the power stroke bycompressing the air trapped therein. This condition would also occur ifthe drill feed direction was reversed such as when pulling the drillsteel out of the hole. Under normal power, the amount of energy impartedto the hammer is usually suflicient to cause extremely high compressionratios in the cushion chamber 58. The resulting temperature increase ofthe trapped air in the chamber 58 is often sufficient to cause ignitionof the drill lubricating oil which is carried by the motive air.

The control valve operates to prevent this condition by substantiallythrottling the motive air supply to the distributing valve 16 in thefollowing manner. As the shank 36 moves out of striking position theseal 78 slides along the tube 66 to the position shown in FIG. 2. Inthis position the compressed air cleaning fluid is cut off from theports 92 and the actuator chamber 96 and annular flow passage 86 arevented to atmosphere through the hole 80 in the chuck driver 30 and thehole 82 in the chuck end housing 54.

A pressure surface on the valve spool 104, being somewhat irregular,allows motive fluid to act thereon to close the valve as shown in FIG.3, thereby substantially throttling the supply of motive fluid to thepercussion motor. Valve closing action is assisted by a coil spring 121acting against the piston 106'.

A small amount of motive air can bypass the closed valve through theport 122 in the valve chest 98 thereby supplying the percussion motorwith enough pressure fluid to idle the piston hammer 14 enough tovibrate the drill for pulling drill steel out of the drill hole but notimparting enough energy to result in high compression ratios in thecushion chamber 58. A suitable idling motive air flow rate is aboutpercent of the full power flow rate.

Therefore, the control system described automatically responds to theshank 36 being out of hammer striking position and throttling of thedrill under this condition is not dependent on the operation of thedrill throttling valve, not shown, which usually is operable only by thedrill operator.

As can be understood from the above description, the control valve wouldalso close in the event of a failure of the tube seal '7 8, orinsuflicient cleaning fluid pressure to keep the valve spool 184 in theopen position. The resulting throttling down of the drill would signalthe operator that one or both malfunctions had occurred.

FIG. 6 illustrates an alternate embodiment of the subject inventioncomprising a mechanical actuator in the form of a cleaning fluid tube124 which is substantially frictionally retained by a tube sealingelement 126 disposed in the bore 64 of the shank 36.

A valve disk 128 is aflixed to the opposite end of the tube 124 andtelescopically receives a fixed section 130 of cleaning fluid tube in abore 132 thereby forming a continuous closed conduit for communicatingdrill hole cleaning fluid to the shank 36. The fixed tube section 130 isretained in the end housing 68 in a manner similar to the embodiment ofFIG. 1.

If the shank 36 moves out of blow receiving relationship with the pistonhammer 14, as illustrated to the right of the axis 7-7 in FIG. 6, thetube 124 and valve disk 128 assembly will be pulled with the shank tothe position shown. Additional biasing force to move the tube and valvedisk assembly is provided by a coil spring 129 acting on the valve disk128.

correspondingly, if the feed force on the drill steel is sufficient tomove the shank 36 to the position shown to the left of the axis 77 inFIG. 6, the tube and valve disk assembly will be moved against thebiasing force of the spring 129 due to the substantial frictionalengagement of the tube 124 by the sealing element 126.

Should the sealing element 126 fail to provide suflicient gripping forceon the tube 124 due to wear or other mal function the valve disk andtube assembly would still be operative since in moving to the positionshown to the left of the axis 77 the shank 36 would engage the lower endof the tube 124 on the surface 131 formed as a shoulder by the reducedbore 62, to push the valve disk and tube assembly upward to the positionshown.

A stepped sleeve 133 is disposed in the housing 10 between thedistributing valve 16 and the motive air inlet port 102 and togetherwith the valve disk 128 forms an annular flow passage with the valvedisk 128 in the position shown to the left of the axis 77 in FIG. 6which has a flow area bound by the disk circumference 134 and the wall136 of the sleeve 133. With the valve disk 128 in the position shown tothe right of the axis 77 in FIG. 6, corresponding to the shank 36 beingout of blow-receiving relation with the piston hammer 14, a secondannular flow passage is formed having an area bound by the diskcircumference 134 and the stepped wall 138. This second flow area beingsubstantially less than the first flow area restricts the flow of motiveair to the distributing valve 16 when the tube 124 together with thevalve disk 128 moves to the position corresponding to the shank beingout of striking position.

The embodiment of FIG. 6 therefore performs the same function as theembodiment of FIGS. 1-5, that being to substantially idle the drillpreventing overheating and ignition in the piston hammer cushion chamberand is particularly useful for drills using water or other liquidcleaning fluid mediums.

It will be apparent to those skilled in the art that the embodimentsshown could be applied equally well to various designs of percussiondrills, for example, those types using rifle bar type rotationmechanisms as opposed to the independent rotation type illustrated.

I claim:

1. In a percussion tool including:

a pressure fluid actuated percussion motor including a housing having acylinder bore and a piston hammer reciprocably disposed therein.

pressure fluid supply means;

tool shank means disposed in one end of said housing and axiallyshiftable into and out of blow receiving relationship with said hammer,said shank means including a longitudinal bore therein; and

control valve means interposed between said pressure fluid supply andsaid percussion motor, said control valve including a pressure fluidactuator responsive to the supply and venting of pressure fluidtherefrom to operate said control valve between a first position forproviding flow of pressure fluid to said percussion motor and a secondposition for reducing flow of pressure fluid to said percussion motor,the improvement comprising:

a member disposed between said shank and said control valve andtelescopically received in said bore in said shank, said member definingin part vent means and conduit means interconnecting said control valveactuator and said shank means for supplying pressure fluid to andventing pressure fluid from said actuator means in response to the axialshifting of said shank means; and

sealing means disposed in said bore of said shank means and sealinglyengageable with said member whereby in response to the axial shifting ofsaid shank means said sealing means interrupts the supply of pressurefluid to said conduit means.

2. The invention according to claim 1 wherein:

said member comprises a double walled tube having a first passage formedby the interior bore of an inner tube and a second passage formed by anannular space between said inner tube and an outer tube;

said first passage comprises means for supplying pressure fluid to saidshank bore; and

said second passage comprises said conduit means interconnecting saidshank means and said actuator means.

3. The invention according to claim 2 wherein:

said vent means comprises aperture means in said outer tube walladjacent said telescopically receivable end of said member whereby inresponse to said shank means axially shifting into blow receivingrelationship with said hammer, pressure fluid is supplied through saidaperture means and said conduit means to said actuator means for movingsaid control valve to said first position and upon said shank meansshifting out of blow receiving relationship with said hammer, saidsealing means becomes interposed between said aperture means and saidpressure fluid supply and said aperture means vents pressure fluid fromsaid conduit and said actuator.

References Cited UNITED STATES PATENTS 897,958 9/1908 Boyer l73153,045,768 7/ 1962 Huffman 173-15 X 3,305,953 2/1967 Von Mehren et al.173-15 X FOREIGN PATENTS 455,988 2/1928 Germany.

ERNEST R. PURSER, Primary Examiner U.S. Cl. X.R. 173--78

